[PATCH] Add -fld-path= to specify an arbitrary executable as the linker
Fāng-ruì Sòng
maskray@google.com
Fri Jul 3 17:18:15 GMT 2020
On 2020-07-03, Martin Liška wrote:
>On 7/2/20 9:34 PM, Fāng-ruì Sòng wrote:
>>On 2020-07-01, Fāng-ruì Sòng wrote:
>>>On 2020-07-01, Martin Liška wrote:
>>>>On 6/30/20 5:32 PM, Fāng-ruì Sòng wrote:
>>>>>There is some concern about clang's -fuse-ld=path
>>>>>http://lists.llvm.org/pipermail/cfe-dev/2020-June/065710.html and use
>>>>>of COMPILER_PATH vs PATH.
>>>>>Shall we introduce another option like -fld-path=path (PATH is used,
>>>>>COMPILER_PATH is not used)?
>>>>
>>>>I would recommend first landing a patch to LLVM and then we can do
>>>>a corresponding change to GCC.
>>>>
>>>>Martin
>>>
>>>Thank a lot for you welcoming words! This is what I intend to add for clang: https://reviews.llvm.org/D83015
>>>
>>>I'll create a GCC patch superseding this one later.
>>
>>Attached the new patch.
>
>Thank you for the update patch:
>
>>From e7f86cdcaf03e4ddb98d0df9d07894d9ffb7d91a Mon Sep 17 00:00:00 2001
>>From: Fangrui Song <maskray@google.com>
>>Date: Thu, 2 Jul 2020 12:26:09 -0700
>>Subject: [PATCH] Add -fld-path= to specify an arbitrary executable as the
>> linker
>>
>>The value can be either a relative path (relative to a COMPILER_PATH
>>directory or a PATH directory) or an absolute path. -fld-path=
>>complements -fuse-ld={bfd,gold,lld} which specifies the linker flavor.
>>
>> PR driver/93645
>> * common.opt (-fld-path=): Add -fld-path=
>> * opts.c (common_handle_option): Handle OPT_fld_path_.
>> * gcc.c (driver_handle_option): Likewise.
>> * collect2.c (main): Likewise.
>> * doc/invoke.texi: Document -fld-path=.
>>---
>> gcc/collect2.c | 57 ++++++++++++++++++++++++++++++++-------------
>> gcc/common.opt | 4 ++++
>> gcc/doc/invoke.texi | 6 +++++
>> gcc/gcc.c | 2 +-
>> gcc/opts.c | 1 +
>> 5 files changed, 53 insertions(+), 17 deletions(-)
>>
>>diff --git a/gcc/collect2.c b/gcc/collect2.c
>>index f8a5ce45994..efa652f7f82 100644
>>--- a/gcc/collect2.c
>>+++ b/gcc/collect2.c
>>@@ -844,6 +844,7 @@ main (int argc, char **argv)
>> const char **ld1;
>> bool use_plugin = false;
>> bool use_collect_ld = false;
>>+ const char *ld_path = NULL;
>> /* The kinds of symbols we will have to consider when scanning the
>> outcome of a first pass link. This is ALL to start with, then might
>>@@ -961,12 +962,21 @@ main (int argc, char **argv)
>> if (selected_linker == USE_DEFAULT_LD)
>> selected_linker = USE_PLUGIN_LD;
>> }
>>- else if (strcmp (argv[i], "-fuse-ld=bfd") == 0)
>>- selected_linker = USE_BFD_LD;
>>- else if (strcmp (argv[i], "-fuse-ld=gold") == 0)
>>- selected_linker = USE_GOLD_LD;
>>- else if (strcmp (argv[i], "-fuse-ld=lld") == 0)
>>- selected_linker = USE_LLD_LD;
>>+ else if (strncmp (argv[i], "-fuse-ld=bfd", 9) == 0
>>+ && selected_linker != USE_LD_MAX)
>>+ {
>
>This does not seem correct to me. You match -fuse-ld=bfd and then
>test other option values in the following block.
This is correct but I probably should use:
- strncmp (argv[i], "-fuse-ld=bfd", 9) == 0
+ strncmp (argv[i], "-fuse-ld=", 9) == 0
>>+ if (strcmp (argv[i] + 9, "bfd") == 0)
>>+ selected_linker = USE_BFD_LD;
>>+ else if (strcmp (argv[i] + 9, "gold") == 0)
>>+ selected_linker = USE_GOLD_LD;
>>+ else if (strcmp (argv[i] + 9, "lld") == 0)
>>+ selected_linker = USE_LLD_LD;
>>+ }
>>+ else if (strncmp (argv[i], "-fld-path=", 10) == 0)
>>+ {
>>+ ld_path = argv[i] + 10;
>>+ selected_linker = USE_LD_MAX;
>>+ }
>> else if (strncmp (argv[i], "-o", 2) == 0)
>> {
>> /* Parse the output filename if it's given so that we can make
>>@@ -1117,14 +1127,27 @@ main (int argc, char **argv)
>> ld_file_name = find_a_file (&cpath, collect_ld_suffix, X_OK);
>> use_collect_ld = ld_file_name != 0;
>> }
>>- /* Search the compiler directories for `ld'. We have protection against
>>- recursive calls in find_a_file. */
>>- if (ld_file_name == 0)
>>- ld_file_name = find_a_file (&cpath, ld_suffixes[selected_linker], X_OK);
>>- /* Search the ordinary system bin directories
>>- for `ld' (if native linking) or `TARGET-ld' (if cross). */
>>- if (ld_file_name == 0)
>>- ld_file_name = find_a_file (&path, full_ld_suffixes[selected_linker], X_OK);
>>+ if (selected_linker == USE_LD_MAX)
>>+ {
>>+ /* If -fld-path= does not contain a slash, search for the command using
>>+ the PATH environment variable. */
>
>We also support file systems like Windows where the comment about a slash will be misleading.
>You can just mention relative vs. absolute path.
The behavior is modeled after
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html Command Search and Execution
e. Otherwise, the command shall be searched for using the PATH environment variable as described in XBD Environment Variables :
is performed if "the command name does not contain any <slash> characters".
For your suggestion, I think 'word' can mean a relative path as well, along with 'rel\path' and 'rel/path'.
Should I say
If -fld-path= does not contain a path component separator (e.g. slash), search for the command using
?
>>+ if (lbasename (ld_path) == ld_path)
>
>Does it really return the same pointer? Maybe strcmp can be needed?
lbasename returns a const char * referencing a place of the string.
lto-wrapper.s has a similar use case:
1542: if (!dumppfx || lbasename (dumppfx) == dumppfx)
>>+ ld_file_name = find_a_file (&path, ld_path, X_OK);
>>+ else if (file_exists (ld_path))
>>+ ld_file_name = ld_path;
>>+ }
>>+ else
>>+ {
>>+ /* Search the compiler directories for `ld'. We have protection against
>>+ recursive calls in find_a_file. */
>>+ if (ld_file_name == 0)
>>+ ld_file_name = find_a_file (&cpath, ld_suffixes[selected_linker], X_OK);
>>+ /* Search the ordinary system bin directories
>>+ for `ld' (if native linking) or `TARGET-ld' (if cross). */
>>+ if (ld_file_name == 0)
>>+ ld_file_name =
>>+ find_a_file (&path, full_ld_suffixes[selected_linker], X_OK);
>>+ }
>> #ifdef REAL_NM_FILE_NAME
>> nm_file_name = find_a_file (&path, REAL_NM_FILE_NAME, X_OK);
>>@@ -1297,9 +1320,11 @@ main (int argc, char **argv)
>> #endif
>> }
>> else if (!use_collect_ld
>>- && strncmp (arg, "-fuse-ld=", 9) == 0)
>>+ && (strncmp (arg, "-fuse-ld=", 9) == 0 ||
>>+ strncmp (arg, "-fld-path=", 10) == 0))
>> {
>>- /* Do not pass -fuse-ld={bfd|gold|lld} to the linker. */
>>+ /* Do not pass -fuse-ld={bfd|gold|lld} or -fld-path= to the
>>+ linker. */
>> ld1--;
>> ld2--;
>> }
>>diff --git a/gcc/common.opt b/gcc/common.opt
>>index df8af365d1b..d5dfbb5c9c6 100644
>>--- a/gcc/common.opt
>>+++ b/gcc/common.opt
>>@@ -2919,6 +2919,10 @@ fuse-ld=lld
>> Common Driver Negative(fuse-ld=lld)
>> Use the lld LLVM linker instead of the default linker.
>>+fld-path=
>>+Common Driver Joined
>>+Use the specified executable instead of the default linker.
>>+
>> fuse-linker-plugin
>> Common Undocumented Var(flag_use_linker_plugin)
>>diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>index e21d8a5217b..bfb6222f96b 100644
>>--- a/gcc/doc/invoke.texi
>>+++ b/gcc/doc/invoke.texi
>>@@ -14651,6 +14651,12 @@ Use the @command{gold} linker instead of the default linker.
>> @opindex fuse-ld=lld
>> Use the LLVM @command{lld} linker instead of the default linker.
>>+@item -fld-path=@var{linker}
>>+@opindex fld-path=linker
>>+Use the specified executable named @var{linker} instead of the default linker.
>>+If @var{linker} does not contain any slash character, the linker will be
>>+searched for using @env{PATH}. This option overrides @option{-fuse-ld=}.
>
>The slash comment applies here as well.
>
>Martin
Ack. Will update when I get a clarification regarding the previous comment.
>>+
>> @cindex Libraries
>> @item -l@var{library}
>> @itemx -l @var{library}
>>diff --git a/gcc/gcc.c b/gcc/gcc.c
>>index c0eb3c10cfd..a57a3d0aec4 100644
>>--- a/gcc/gcc.c
>>+++ b/gcc/gcc.c
>>@@ -1077,7 +1077,7 @@ proper position among the other output files. */
>> LINK_PLUGIN_SPEC \
>> "%{flto|flto=*:%<fcompare-debug*} \
>> %{flto} %{fno-lto} %{flto=*} %l " LINK_PIE_SPEC \
>>- "%{fuse-ld=*:-fuse-ld=%*} " LINK_COMPRESS_DEBUG_SPEC \
>>+ "%{fuse-ld=*:-fuse-ld=%*} %{fld-path=*:-fld-path=%*} " LINK_COMPRESS_DEBUG_SPEC \
>> "%X %{o*} %{e*} %{N} %{n} %{r}\
>> %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!r:%{!nostartfiles:%S}}} \
>> %{static|no-pie|static-pie:} %@{L*} %(mfwrap) %(link_libgcc) " \
>>diff --git a/gcc/opts.c b/gcc/opts.c
>>index 340d99434b3..c4507d53abc 100644
>>--- a/gcc/opts.c
>>+++ b/gcc/opts.c
>>@@ -2750,6 +2750,7 @@ common_handle_option (struct gcc_options *opts,
>> case OPT_fuse_ld_bfd:
>> case OPT_fuse_ld_gold:
>> case OPT_fuse_ld_lld:
>>+ case OPT_fld_path_:
>> case OPT_fuse_linker_plugin:
>> /* No-op. Used by the driver and passed to us because it starts with f.*/
>> break;
>>--
>>2.27.0.383.g050319c2ae-goog
>>
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